I was an undergraduate student the first time I heard about counterfactual history, and it was in connection with the crisis that led to the outbreak of the Great War, or World War I. I remember a history professor of mine referring with intellectual disdain to the question “What would have happened if Gavrilo Princip had failed to kill the Archduke Franz Ferdinand?” World War I would have erupted in any event, sooner or later, he went on to say. My conclusion, after hearing his comment, was that counterfactual history was intellectually irrelevant if not wholly unacceptable.

Many of my own students today express their dismay when I resort to counterfactual history in my classes. They have been taught that what counts is what actually happened and not what might have happened. They ask, “Isn’t the query ‘What would have happened if X or Y had not taken place?’ beyond the academic domain of the serious historian?”

To be sure, that’s exactly what I used to think when I was their age. I no longer do.

In order to argue my case in favor of counterfactual history, I explain to them the difference between science fiction and counterfactual history.

For instance, the question “What would have happened had a meteorite fallen on Gavrilo Princip a few minutes before he managed to kill the Archduke Franz Ferdinand and his wife, Sophie?” is not counterfactual history, but science fiction.

However, the question “What would have happened if Gavrilo Princip had failed in his assassination attempt?” is counterfactual history and not science fiction.

Counterfactual history is not science fiction because it is based on a series of events that did happen and asks a question about something that might have happened differently. The variables employed are not fictional. The assumptions entertained are not illusory.

Contrary to what I thought when I was a student, and to what many of my own students believe, counterfactual history is not designed to depict a scenario that could not have happened, but rather one that might have happened.

The aim is not to change history, as is wrongly assumed. Rather, the objective is to understand it better. In other words, counterfactual history is a device aimed at comprehending better the role of the different actors in the story being studied. Also, it is a means to comprehend the importance of chance or accident in human affairs.

Counterfactual history is anathema to those who believe in historical determinism. After all, if one believes that things are preordained or follow a certain coherent pattern toward a predetermined end, a scenario entailing a different turn of events is unlikely to be entertained lightly. Even if events might be countenanced to have evolved differently than they actually were, their importance in changing historical processes would be discounted.

Counterfactual history is based on the assumption that events are not preordained and that individuals are not actors playing a role without being aware of it. Certainly, circumstances may limit their scope of decision and constrain their freedom of action. However, on the whole, decision makers are thought to be free agents and their decisions the corollary of choice. Counterfactual history would be irrelevant if one were to assume otherwise.

To be sure, the question “What would have happened if X or Y had not occurred?” should not necessarily lead to the depiction of a wholly different scenario from the one that is already known. In other words, one might actually reach the conclusion that the outcome might have been similar to the one we know about.

For instance, if we asked what would have happened had Gavrilo Princip failed in his attempt to kill Archduke Franz Ferdinand, and then answered that World War I might have erupted anyway, sooner or later, we could still be engaging in counterfactual history.

The “what if” question in this case could lead to an implied conclusion that the role played by Gavrilo Princip in the crisis leading to World War I was not crucial. He was not the motive but rather the instigator of a process that culminated in the outbreak of World War I. His action was the trigger of the crisis that led to war, not its real cause. Thus, any other trigger might have led to the same outcome, according to this analysis.

Of course, assuming that events would have unfolded, in one way or another, in a similar vein could imply a deterministic attitude. Thus, according to this scenario, World War I would have erupted with or without the personal intervention of Gavrilo Princip.

In this context, it is important to stress the difference between a deterministic and a probabilistic analytical perspective. The first negates, whereas the latter allows for contingency. Thus, saying that World War I would have occurred anyway denotes a deterministic analytical perspective. However, arguing that World War I might have occurred reflects a probabilistic analytical perspective.

Gavrilo Princip himself is reported to have engaged in counterfactual history. Asked in prison a few years subsequently how he felt about being responsible for the death of so many people, he replied that had he not done what he did Germany would have found another excuse to start the war.

Yoav Tenembaum is a lecturer in the Diplomacy Program at Tel Aviv University.